Add sub and super vertical align values

[TCatinaud]

Hi,
I would add .align-sub and .align-super classes.

Udpate verticalAlign.js

'.align-sub': { 'vertical-align': 'sub' },
'.align-super': { 'vertical-align': 'super' },

[codecov-io]

Codecov Report

Merging #2910 (4a0c2b6) into master (3ea5e18) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2910   +/-   ##
=======================================
  Coverage   93.20%   93.20%           
=======================================
  Files         177      177           
  Lines        1795     1795           
  Branches      317      317           
=======================================
  Hits         1673     1673           
  Misses        105      105           
  Partials       17       17           

Impacted Files	Coverage Δ
src/plugins/verticalAlign.js	100.00% <ø> (ø)

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[SimonJnsson]

Would like to see this merged aswell

[adamwathan]

Hey thanks! I've reworked this as #5486 due to merge conflicts but have included you as a co-author on the commit to ensure you get credit ❤️